WARNING: MASSIVE SPOILERS TO COME. If you haven't yet seen Looper, then you shouldn't be here. And, if possible, you should travel back to the start of the weekend and tell your past self to catch the next showing. It lost the box office to Hotel Transylvania. Seriously? Trust us: It'll be worth your, err... time. DISCLAIMER: We are not here to ruin anyone's movie-going fun. We greatly enjoyed Looper. But we are here to fry your brain like an egg. It's kind of our thing. A detailed analysis of Looper's time travel whys and wherefores is to follow. Just keep in mind that delving into the details is one reason we love time travel movies, so don't take our showcasing of inevitable plot holes as an indictment of the film. So break out your diner straws. It's time to make some diagrams. The Rules
The only fair way to examine a time travel movie is to follow the rules the movie itself sets up. You can take issue with the method (Superman flying backwards around the Earth, the Enterprise slingshotting around the sun, etc.), but from there a simple examination of causality will reveal all you need to know about the time travel trickery at work. On this front, Looper mostly does a good job. Here's what we know:
Rule 1: There is a single timeline
This is made clear by the fact that alterations to Young Seth's body instantly manifest in Old Seth. And, when Young Joe carves "BEATRIX" into his arm, it instantly appears on Old Joe as a gruesome scar. Rule 2: Sending someone to the past creates a divergent timeline This is made clear by the the quick peek of Joe's life in which he does "close his loop" (that is, he kills his future self, played by Bruce WIllis). It's different than the one he experiences in the story of the film. Put another way: time travel to the past obliterates the pre-existing timeline. Even though it still happened, you can't get it back. Typically, this isn't as alarming as it sounds. When an old looper is sent to the past to close their loop, for example, no alterations take place. Where it gets messy is when, say, Seth or Joe let their loop run. Then the life that Old Joe experienced (which we see in a rapid montage through 30 years) is suddenly gone. And the one that Young Joe experiences will be something different. Probably. The movie also accepts that there is a certain degree of probability built into everyone's life. This is why Old Joe's memories aren't instantly obliterated the moment he arrives in the past and socks Young Joe in the face, even though Old Joe has made a huge change to the course of Young Joe's life. As events become more certain (or occur), they displace Old Joe's memories. We see that Old Joe is still able to hold on to the memory of his wife, because the events he has altered haven't yet disallowed for their meeting in the future. If he were to change something critical to their meeting, like, as Young Joe tells him, showing Young Joe her photo, so that he is able to avoid her in the future, Old Joe's memory of her would be instantly eradicated. It's like Marty McFly's family polaroid in Back To The Future -- it fades slowly as events play out and become less likely. Always changing, the future is. (Oh, now you get it.) This leads us to a third rule, born naturally from the first two: Rule 3: Paradoxes are not possible
The Looper universe is self-correcting (see Rule 1). And, even when a divergent timeline is created (like when Old Joe comes back and runs), the previous timeline still occurred. It preceded and was necessary to set up the new, divergent timeline (see Rule 2). In the film itself, we experience two timelines. The timeline of Old Joe, which we see via montage, and the timeline of Young Joe, where the story of the film takes place. But the movie implies at least two preceding timelines. Let's lay them all out so that we can see how the rules manifest and how time works in Looper's universe. The...